Back.
Remember that tiny bulge I found near the breach of my copper barrel? Yeah, it got a little bigger. So, are we calling this DDT or just the consequence of using copper tubing at pressures above what they're intended for? The projectile for the shot in question at a 10x mix was a 42g fishing sinker with a loose-ish fit in the barrel so had a foam sabot accompanying it.
I had previously got in to the habit of avoiding holding the barrel of this hybrid and the new chamber configuration made sure my hand was well clear. It was the loudest shot by far that I've ever heard from this cannon (probably due to the report exiting at the side instead of pointed away from me) and I fell over on my ass (probably from shock) from a kneeling stance for a measly ~1000ft/lbs of muzzle energy.
There is a video, doesn't show a whole lot but it'll be up some time this week I assume.
Edit:
jackssmirkingrevenge wrote:We've had this conversation before, the sabot is most likely breaking up inside the barrel. What of those compressed foil sabots I had recommended

I actually found some sabot after a particular shot. There were two large pieces that would combine to make 90% of the sabot, so I don't think the foam is too bad until I find something better to use.